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1.
This study deals with transport of solutes through a saturated sub-surface rock formation with well-defined horizontal parallel fractures. For this purpose, a simplified conceptual model consisting of a single fracture and its associated rock-matrix is considered in the presence of a fracture-skin in order to study the mobility and mixing of solutes along the fracture. In this paper, a coupled fracture-skin-matrix system is modeled numerically using finite difference method in a pseudo two-dimensional domain with a constant continuous source at fracture inlet. Flow and transport processes are considered parallel to the fracture axis, while the transport processes in fracture-skin as well as in rock-matrix are considered perpendicular to the fracture axis. Having obtained the concentration distribution along the fracture, method of spatial moments is employed to study the mobility and spreading of solutes. Sensitivity analyses have been done to understand the effect of various fracture-skin parameters like porosity, thickness, and diffusion coefficient. Further, the influence of non-linear sorption and radioactive decaying of solutes are carried out for different sorption intensities and decay constants. Results suggest that the presence of fracture-skin significantly influences the mobility and spreading of solutes along the fracture in comparison with a coupled fracture-matrix system without fracture-skin. 相似文献
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A numerical model is developed for describing the transport of virus in a fracture-matrix coupled system with fracture-skin.An advective dispersive virus transport equation,including firstorder sorption and inactivation constant is used for simulating the movement of viruses.Implicit finite-difference numerical technique is used to solve the coupled non-linear governing equations for the triple continuum model consisting of fracture,fracture-skin and the rock-matrix.A varying grid is adopted at the fracture and fracture-skin interface to capture the mass transfer.Sensitivity analysis was performed to investigate the effect of various properties of the fracture-skin as well as viruses on the virus concentration in the fractured formation with fracture-skin.Simulation results suggest that the virus concentration in the fracture decreases with increment in the fracture-skin porosity,fracture-skin diffusion coefficient,mass transfer coefficient,inactivation constant and sorption distribution coefficient, and with reduction in the fracture aperture. 相似文献
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A numerical model is developed for investigating the evolution of fracture permeability in a coupled fracture-matrix system in the presence of fracture-skin with simultaneous colloidal and bacterial tr... 相似文献
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为探究盐、热示踪剂在裂隙-基质中示踪的有效性,设计了充填裂隙-基质试验模型,开展了不同示踪剂下的试验,结合不同测点的实时动态电阻率监测数据,研究充填裂隙-基质中示踪剂运移过程,并讨论基于电阻率法的盐、热示踪的有效性结果表明：（1）电阻率法可以揭示3种不同示踪剂注入充填裂隙-基质系统的过程以及裂隙-基质系统中裂隙的存在;（2）盐热示踪剂下裂隙与基质内的体积电导率变化率差异最为显著;（3）质量浓度与体积电导率拟合效果要优于温度与体积电导率拟合效果。这说明了基于电阻率法的示踪剂对刻画裂隙-基质中裂隙与基质位置的有效性,且盐热联合示踪剂效果最好。数据成果对野外电法勘探裂隙位置及其他非均质地层构造研究具有一定的参考价值。 相似文献
5.
Based on the combined finite-discrete element method (FDEM), a two-dimensional coupled hydro-thermal model is proposed. This model can simulate fluid flow and heat transfer in rock masses with arbitrary complex fracture networks. The model consists of three parts: a heat conduction model of the rock matrix, a heat-transfer model of the fluid in the fracture (including the heat conduction and convection of fluid), and a heat exchange model between the fluid and rock at the fracture surface. Three examples with analytical solutions are given to verify the correctness of the coupled model. Finally, the coupled model is applied to hydro-thermal coupling simulations of a rock mass with a fracture network. The temperature field evolution, the effect of thermal conductivity of the rock matrix thermal conductivity and the fracture aperture on the outlet temperature are studied. The coupled model presented in this paper will enable the application of FDEM to study rock rupture driven by the effect of hydro-thermo-mechanical coupling in geomaterials such as in geothermal systems, petroleum engineering, environmental engineering and nuclear waste geological storage.
相似文献6.
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Seepage-heat transfer coupling process of low temperature return water injected into geothermal reservoir in carbonate rocks in Xian County,China 
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下载免费PDF全文 WANG Yan LIU Yan-guang BIAN Kai ZHANG Hong-liang QIN Shen-jun WANG Xiao-jun 《地下水科学与工程》2020,8(4):305-314
Fracture seepage and heat transfer in the geothermal reservoir of carbonate rocks after the reinjection of low temperature geothermal return water is a complex coupling process,which is also the frontier of geothermal production and reinjection research. Based on the research of cascade comprehensive development of geothermal resources in Beijing-Tianjin-Hebei (Xian County),the carbonate geothermal reservoir of Wumishan formation in the geothermal field in Xian County is investigated. With the development of the discrete fracture network model and the coupling model of seepage and heat transfer,the numerical solution of seepage field and temperature field with known fracture network is reached using the finite element software COMSOL,and the coupling process of seepage flow and heat in carbonate rocks is revealed. The results show that the distribution of temperature field of fractured rocks in geothermal reservoir of carbonate rocks has strong non-uniformity and anisotropy. The fracture network is interpenetrated,which constitutes the dominant channel of water conduction,and along which the fissure water moves rapidly. Under the influence of convective heat transfer and conductive heat transfer,one of the main factors to be considered in the study of thermal breakthrough is to make the cold front move forward rapidly. When the reinjection and production process continues for a long time and the temperature of the geothermal reservoir on the pumping side drops to a low level,the temperature of bedrocks is still relatively high and continues to supply heat to the fissure water,so that the temperature of the thermal reservoir on the pumping side will not decrease rapidly to the water temperature at the inlet of reinjection,but will gradually decrease after a long period of time,showing an obvious long tail effect. The distribution of fractures will affect the process of seepage and heat transfer in carbonate reservoirs,which should be considered in the study of fluid thermal coupling in carbonate reservoirs. 相似文献
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In this paper, a fully coupled thermo-hydro-mechanical model is presented for two-phase fluid flow and heat transfer in fractured/fracturing porous media using the extended finite element method. In the fractured porous medium, the traction, heat, and mass transfer between the fracture space and the surrounding media are coupled. The wetting and nonwetting fluid phases are water and gas, which are assumed to be immiscible, and no phase-change is considered. The system of coupled equations consists of the linear momentum balance of solid phase, wetting and nonwetting fluid continuities, and thermal energy conservation. The main variables used to solve the system of equations are solid phase displacement, wetting fluid pressure, capillary pressure, and temperature. The fracture is assumed to impose the strong discontinuity in the displacement field and weak discontinuities in the fluid pressure, capillary pressure, and temperature fields. The mode I fracture propagation is employed using a cohesive fracture model. Finally, several numerical examples are solved to illustrate the capability of the proposed computational algorithm. It is shown that the effect of thermal expansion on the effective stress can influence the rate of fracture propagation and the injection pressure in hydraulic fracturing process. Moreover, the effect of thermal loading is investigated properly on fracture opening and fluids flow in unsaturated porous media, and the convective heat transfer within the fracture is captured successfully. It is shown how the proposed computational model is capable of modeling the fully coupled thermal fracture propagation in unsaturated porous media. 相似文献
9.
Poro‐mechanical and thermo‐mechanical processes change the fracture aperture and thus affect the water flow pattern in the fracture during the cold water injection into enhanced geothermal systems (EGS). In addition, the stresses generated by these processes contribute to the phenomenon of reservoir seismicity. In this paper, we present a three‐dimensional (3D) partially coupled poro‐thermoelastic model to investigate the poroelastic and thermoelastic effects of cold water injection in EGS. In the model, the lubrication fluid flow and the convective heat transfer in the fracture are modeled by the finite element method, while the pore fluid diffusion and heat conductive transfer in the reservoir matrix are assumed to be 3D and modeled by the boundary integral equation method without the need to discretize the reservoir. The stresses at the fracture surface and in the reservoir matrix are obtained from the numerical model and can be used to assess the variation of in situ stress and induced seismicty with injection/extraction. Application of the model shows that rock cooling induces large tensile stresses and increases fracture conductivity, whereas the rock dilation caused by fluid leakoff decreases fracture aperture and increases compressive total stresses around the injection zone. However, increases in pore pressure reduce the effective stresses and can contribute to rock failure, fracture slip, and microseismic activity. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
10.
Seyed Erfan Saberhosseini Reza Keshavarzi Kaveh Ahangari 《Arabian Journal of Geosciences》2017,10(6):152
One of the crucial consequences of steam assisted gravity drainage (SAGD) process is abnormal reservoir uplifting under thermal steam injection, which can significantly influence the reservoir rock deformation, specifically thin bed reservoirs and causes intensive failures and fractures into the cap rock formations. A thorough understanding of the influences of rock thermo-mechanical properties on reservoir uplifting plays an important role in preventing those aforementioned failures within design and optimization process in SAGD. In addition, coupling of reservoir porous medium and flowing of specific fluid with temperature as an additional degree of freedom with initial pore pressure and in-situ stress condition, are also very challenging parts of geomechanical coupled simulation which would be clearly explained. Thus, a fully coupled thermo-poro-elastic geomechanical model with finite element codes was performed in ABAQUS to investigate the role of rock thermo-mechanical parameters on reservoir vertical uplift during steam injection. It is clearly observed that, any increase in rock thermo-mechanical properties specifically rock’s thermal properties such as specific heat, thermal expansion, and formation’s thermal conductivity, have significant influences on reservoir uplift. So by coupling the temperature as an additional degree of freedom with the coupled pore-fluid stress and diffusion finite element model of SAGD process, the more realistic simulation will be conducted; hence, the errors related to not having heat as an additional degree of freedom will be diminished. In addition, Young’s modulus and specific heat are the rock thermo-mechanical parameters which have the maximum and minimum effects on the reservoir uplift, respectively. 相似文献